In a corrugator for making corrugated paperboard, there is provided a double facer machine and at least one single facer machine. Each of said machines processes two webs. At least one web processed by each machine is preheated by peripheral contact with a heated drum. The heated drum and its associated elements constitutes a preheater.
A preheater for heating a web moving in a paperboard corrugator includes a frame supporting a drum. The drum is supported for rotation about the longitudinal axis thereof and is constructed to transmit heat to a web in surface contact therewith. First and second idler rollers are supported by the frame for movement about the periphery of said drum for effecting the wrap of the web over the surface of said drum. A drive means is provided including a motor responsive to changes in the speed of the web in the corrugator for causing said first and second idler rollers to move between a minimum wrap position and a maximum wrap position as the speed of the web varies from a minimum to a maximum.
At a control panel, an operator may select a speed which is indicative of the lowermost position for the idler rollers. In the lowermost position of the idler rollers, maximum heat is transferred to the web. The position of the idler rollers is moved automatically relative to the drum axis in proportion to changes in web speed to maintain a uniform transfer of heat to the web.
A voltage sensitive relay is coupled across first and second potentiometers. One such potentiometer is part of the speed setting means of the drive power unit for the single facer machine or the double facer machine. The other potentiometer is coupled to a motor to effect up and down movement of the idler rollers. If the speed of the single facer machine decreases, the voltage-sensitive relay will detect it and cause the idler rollers to move upward so as to decrease the wrap of the web on the drum and thus decrease the amount of heat transferred to the web and vice versa. Thus, the position of the idler rollers is automatically responsive to a reference speed signal indicative of the speed of the single facer machine or double facer machine which in turn corresponds to web speed.
It is an object of the present invention to provide a novel preheater.
It is another object of the present invention to provide a preheater wherein the amount of wrap is varied as a function of web speed.
It is another object of the present invention to provide a preheater which may be used in conjunction with a single facer machine or double facer machine to control the amount of wrap as a function of web speed.
It is another object of the present invention to provide a preheater which is relatively simple, inexpensive, and reliable for use in an automated corrugator for producing corrugated paperboard.
Other objects will appear hereinafter.